1. Field of the Invention
The present invention relates to a bending operation system.
2. Description of the Related Art
There is known, for example, a device having a tubular portion such as an endoscope or a manipulator which has a bending portion capable of a bending operation. In the endoscope or manipulator having such an operable bending portion, a wire is connected to the bending portion, and the bending portion is configured to be bent by the pulling of the wire. For example, a technique related to an endoscope is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 61-087530, and this endoscope is provided with two wires each connected at one end to the vicinity of a bending portion. These two wires are displaced by a drum of an operation portion to which the other ends of the two wires are fixed, whereby the bending portion is bent.
In the endoscope or the manipulator disclosed in Jpn. Pat. Appln. KOKAI Publication No. 61-087530, it is possible that operation assist information is acquired in order to improve operability. For example, it is presumable to acquire an operation amount showing the shape of the bending portion or an operation amount of the operation portion as the operation assist information.
For example, one way of acquiring the operation assist information is to dispose an angle sensor in the bending portion, thereby measuring a bending amount of the bending portion. However, the bending portion is increased in size because of the angle sensor disposed in the bending portion and because of a wiring line for the angle sensor. For example, when it is intended for a tubular portion having this bending portion to be inserted into a narrow tube, the bending portion needs to be reduced in size. Conversely, however, disposing the angle sensor or the like in the bending portion is disadvantageous for size reduction of the tubular portion.
On the other hand, it is presumable that a displacement of the wire for driving the bending portion is acquired by, for example, an encoder, and operation assist information such as a bending amount of the bending portion is calculated on the basis of the displacement. However, the displacement of the wire and, for example, the bending amount of the bending portion are not in one-to-one correspondence sometimes. In this case, if a bending amount is calculated from the displacement of the wire on the basis of a function in which the displacement of the wire and the bending amount of the bending portion are in one-to-one correspondence, there is a possibility that the calculated bending amount may be different from an actual bending amount.